Here's a sample ePub. It includes four images. ADE will display the first and last image, but not the two middle images. It seems to be tied to the image - I have fifteen similar images, and it's only these two that ADE won't display.

It must be something to do with the image, but I can't spot what the difference is. Does anyone have any bright ideas?

Jellby

09-03-2009, 12:33 PM

Sorry, no idea there...

So, if you change the order to 2, 1, 4, 3... are images 2 and 3 still not shown? or is it now the middle ones (1 and 4)? The only mildly significant different I can find between the images is the jpeg quality:

1: Quality: 90
2: Quality: 95
3: Quality: 94
4: Quality: 96

But I don't see a reason why quality 95 and 94 would not work and 90 and 96 would... Can you try storing all the images with the same quality or altering the sizes a few pixels?

pdurrant

09-03-2009, 01:06 PM

Yes, if the order is changed to be 2,1,4,3, then images 2 and 3 are still not displayed.

I have re-converted the images a couple of times now (once to fix a CMYK->RGB conversion problme and once to fix a trim problem).

On the first re-conversion only one completely different image didn't work. On the second reconversion, one of the non-working images here again didn't work.

I'm mystified. I'll probably just tweak the images until they show up, but I'd be much happier knowing why.

I suppose I could submit it as a bug report to Adobe.... if only they were as responsive as Valloric!

Sorry, no idea there...

So, if you change the order to 2, 1, 4, 3... are images 2 and 3 still not shown? or is it now the middle ones (1 and 4)? The only mildly significant different I can find between the images is the jpeg quality:

1: Quality: 90
2: Quality: 95
3: Quality: 94
4: Quality: 96

But I don't see a reason why quality 95 and 94 would not work and 90 and 96 would... Can you try storing all the images with the same quality or altering the sizes a few pixels?

kovidgoyal

09-03-2009, 01:37 PM

IIRC ADE has a bug that prevents it from displaying certain JPEG files. For example in calibre I found that JPEG files output by the Python Imaging library would often not display in ADE, while the same file if re-converted and output using Qt would.

pdurrant

09-03-2009, 01:39 PM

I'm pleased to hear it's not just me, sort-of.

It sounds as if my best bet is to convert the images as well as I can, and then do invisible tweaks to any files that don't display until they do display. Ughh...

IIRC ADE has a bug that prevents it from displaying certain JPEG files. For example in calibre I found that JPEG files output by the Python Imaging library would often not display in ADE, while the same file if re-converted and output using Qt would.

Ankh

09-03-2009, 03:54 PM

It sounds as if my best bet is to convert the images as well as I can, and then do invisible tweaks to any files that don't display until they do display. Ughh...

For some odd reason, this is very easy with GIMP, load the image, "save as->jpeg", it always works. Have no idea what is that GIMP fixes, but ADE never has problems after this "fix".

I had problems only with jpeg images.

JSWolf

09-03-2009, 10:28 PM

I re-saved the images using Photoshop and all display fine now in ADE for Windows.

I re-saved just images 2 and 3 (quality: 95) and it now works, like JSWolf's solution.

I sometimes have the same problem when converting .prc/.epub ebooks to .imp as the eBook Publisher software I use cannot read some .jpeg's as well. I've never understood why, but just re-saving them with IrfanView has ALWAYS worked for me.

When I wrote my Mobi2IMP conversion software in Perl, I used GD::Image tools to just resave the images extracted from .prc/.mobi ebooks and used those to produce the .imp ebook conversion. Again ALWAYS worked for me! :thumbsup:

Jellby

09-04-2009, 05:15 AM

Of course, you all know re-saving a JPG image as JPG again will only reduce the quality (even if you save it with a higher "quality" setting), so this should be done with the starting source images (either scanned, or large JPGs, or whatever).

Valloric

09-04-2009, 11:56 AM

I re-saved the images using Photoshop and all display fine now in ADE for Windows.

It would be funny if JPEG images produced by Photoshop would fail in ADE... in a frightening sort of way.

Ankh

09-05-2009, 09:45 AM

Of course, you all know re-saving a JPG image as JPG again will only reduce the quality (even if you save it with a higher "quality" setting), so this should be done with the starting source images (either scanned, or large JPGs, or whatever).

True, but it opens up a question of how far we are ready to go with the quality of raster images?

The current technology for screens of dedicated reader devices is what it is. On 600x800 eInk screens, the loss is negligible. For those who read ePubs on computer screens, the situation is quite different.

Now, considering the perfectly probable emergence of high-resolution, full-colour screens for mobile devices a decade from now, do you go with the maximum resolution (and quality) for materials that you scan, future-proofing your publication? Lossless compression?

UniversalisPub

09-05-2009, 10:02 AM

Now, considering the perfectly probable emergence of high-resolution, full-colour screens for mobile devices a decade from now, do you go with the maximum resolution (and quality) for materials that you scan, future-proofing your publication? Lossless compression?

And how do you deal with the problem of a 10KB ebook that grows to 100KB just because you've put a cover image into it? A cover image is, after all, purely ornamental and has no semantic value.

I suspect that a more radical solution will have to be found in the end. We might end up including lo-res images in the ePub itself, with links to high-quality ones. Some sort of intelligent loader could then replace the images if the ePub were being loaded into a high-resolution device.